Method and device for fischer-tropsch synthesis

ABSTRACT

A method for Fischer-Tropsch synthesis, the method including: 1) gasifying a raw material to obtain a crude syngas including H 2 , CO and CO 2 ; 2) electrolyzing a saturated NaCl solution using a chloralkali process to obtain a NaOH solution, Cl 2  and H 2 ; 3) removing the CO 2  in the crude syngas using the NaOH solution obtained in 2) to obtain a pure syngas; and 4) insufflating the H 2  obtained in 2) to the pure syngas to adjust a mole ratio of CO/H 2  in the pure syngas, and then introducing the pure syngas for Fischer-Tropsch synthesis reaction. A device for Fischer-Tropsch synthesis includes a gasification device, an electrolyzer, a first gas washing device, and a Fischer-Tropsch synthesis reactor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of International PatentApplication No. PCT/CN2016/079381 with an international filing date ofApr. 15, 2016, designating the United States, now pending, and furtherclaims foreign priority to Chinese Patent Application No. 201510311714.9filed Jun. 9, 2015. The contents of all of the aforementionedapplications, including any intervening amendments thereto, areincorporated herein by reference. Inquiries from the public toapplicants or assignees concerning this document or the relatedapplications should be directed to: Matthias Scholl P.C., Attn.: Dr.Matthias Scholl Esq., 245 First Street, 18th Floor, and Cambridge, Mass.02142.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a method and device forFischer-Tropsch synthesis.

Description of the Related Art

Conventionally, the hydrogen/carbon ratio in the syngas produced fromcoal or biomass is relatively low and such syngas cannot be directlyused for Fischer-Tropsch synthesis. The relatively low amount ofhydrogen leads to low efficiency and low catalyst regeneration level.

Typically, the hydrogen/carbon ratio of the crude syngas is adjusted byusing water-gas shift and decarburization process. The process is longand costly, involves complex steps, and produces a relatively largeamount of greenhouse gases, including CO₂.

SUMMARY OF THE INVENTION

It is one objective of the present disclosure to provide a method anddevice for Fischer-Tropsch synthesis. The method and device improve thehydrogen/carbon ratio in the syngas, and decrease the emission ofgreenhouse gases, including CO₂.

To achieve the above objective, in accordance with one embodiment of thepresent disclosure, there is provided a method for Fischer-Tropschsynthesis, the method comprising:

-   -   1) gasifying a raw material to obtain a crude syngas comprising        H₂, CO and CO₂;    -   2) electrolyzing a saturated NaCl solution using a chloralkali        process to obtain a NaOH solution, Cl₂ and H₂;    -   3) removing the CO₂ from the crude syngas using the NaOH        solution obtained in 2) to obtain a pure syngas; and    -   4) insufflating the H₂ obtained in 2) to the pure syngas to        adjust a mole ratio of CO/H₂ in the pure syngas, and then        introducing the pure syngas for Fischer-Tropsch synthesis        reaction.

In a class of this embodiment, in 3), the CO₂ dispersed in the crudesyngas is removed during a direct gas-liquid contact between the NaOHsolution and the crude syngas yielding the pure syngas.

In a class of this embodiment, in 3), the CO₂ is first separated fromthe crude syngas to yield pure syngas, and then the CO₂ is absorbedusing the NaOH solution.

In a class of this embodiment, in 3), a remaining of the NaOH solutionafter absorbing CO₂ in the crude syngas, is condensed and crystallizedas a by-product.

In a class of this embodiment, in 3), a remaining of the NaOH solutionafter absorbing CO₂ in the crude syngas, is used for removing CO₂ in anindustrial waste gas or gases generated in other processes.

In a class of this embodiment, in 4), a mole ratio of CO/H₂ in the puresyngas is adjusted to 1:1.5 to 2.5.

In a class of this embodiment, in 1), the components of the obtainedcrude syngas are controlled to CO: 5-60%, H₂: 5-45%, CO₂: 5-30% on a drybasis, and the balance is inevitable impurity gases.

In a class of this embodiment, in 1), the raw material is coal, biomass,heavy oil, natural gas, agroforestry waste, household waste, or amixture thereof.

A device for Fischer-Tropsch synthesis designed to realize the aboveprocess comprises a gasification device, an electrolyzer, a first gaswashing device, and a Fischer-Tropsch synthesis reactor, where a syngasoutlet end of the gasification device is connected to a gas inlet of thefirst gas washing device via the pipe system, and a gas outlet of thefirst gas washing device is connected to a feed gas inlet of theFischer-Tropsch synthesis reactor via the pipe system; a hydrogen outletof the electrolyzer is also connected to the feed gas inlet of theFischer-Tropsch synthesis reactor via the pipe system, and a causticsoda solution outlet of the electrolyzer is connected to a washingsolution inlet of the first gas washing device via the pipe system.

In a class of this embodiment, the caustic soda solution outlet of theelectrolyzer is further connected to a washing solution inlet of asecond gas washing device via the pipe system, a gas inlet of the secondgas washing device is connected to a pipe conveying flue gas or otherCO₂-containing gases, and a gas outlet of the second gas washing deviceis connected to a downstream process pipe or atmosphere.

In a class of this embodiment, the gas washing device is a packed tower,a sieve plate tower or a spray tower.

Another device for Fischer-Tropsch synthesis designed to realize theabove process comprises a gasification device, an electrolyzer, adecarburization device, a first gas washing device and a Fischer-Tropschsynthesis reactor, where a syngas outlet end of the gasification deviceis connected to a crude syngas inlet of the decarburization device viathe pipe system, a pure syngas outlet of the decarburization device isconnected to a feed gas inlet of the Fischer-Tropsch synthesis reactorvia the pipe system, and a carbon dioxide outlet of the decarburizationdevice is connected to a gas inlet of the first gas washing device viathe pipe system; a hydrogen outlet of the electrolyzer is also connectedto the feed gas inlet of the Fischer-Tropsch synthesis reactor via thepipe system, and a caustic soda solution outlet of the electrolyzer isconnected to a washing solution inlet of the first gas washing devicevia the pipe system.

In a class of this embodiment, the caustic soda solution outlet of theelectrolyzer is further connected to a washing solution inlet of asecond gas washing device via the pipe system, a gas inlet of the secondgas washing device is connected to a pipe conveying flue gas or otherCO₂-containing gases, and a gas outlet of the second gas washing deviceis connected to a downstream process pipe or atmosphere.

In a class of this embodiment, the gas washing device is a packed tower,a sieve plate tower or a spray tower.

In a class of this embodiment, the decarburization device is a pressureswing adsorption device or a low-temperature methanol washing device.

Advantages of the method and device for Fischer-Tropsch synthesisaccording to embodiments of the present disclosure are summarized asfollows.

Firstly, the present invention introduces chloralkali to Fischer-Tropschsynthesis process, organically combines the chloralkali process withFischer-Tropsch synthesis, adjusts the composition of pure syngas in theFischer-Tropsch synthesis process using hydrogen that is a product ofchloralkali, so as to meet the gas intake requirements ofcarbon/hydrogen mole ratio (CO/H₂) in the syngas for Fischer-Tropschsynthesis reaction, thereby simplifying treatment of water-gas shiftprocess, and achieving the purpose of simplifying or eliminatingconversion process in the Fischer-Tropsch synthesis.

Secondly, the present invention also removes carbon dioxide from thecrude syngas through contact between caustic soda solution that isanother product of chloralkali and the CO₂-containing crude syngas,which not only has important significance for reducing emissions ofgreenhouse gases, but also economically and efficiently uses chloralkaliproducts.

Thirdly, the device of the present invention simplifies the conversionprocess in the Fischer-Tropsch synthesis process, and greatly improvesthe economic efficiency of the Fischer-Tropsch synthesis process anddevice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram of a device for Fischer-Tropsch synthesisin accordance with one embodiment of the present invention; and

FIG. 2 is a modified structure of a device for Fischer-Tropsch synthesisin FIG. 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

For further illustrating the invention, experiments detailing a methodand device for Fischer-Tropsch synthesis are described below. It shouldbe noted that the following examples are intended to describe and not tolimit the invention.

FIG. 1 shows a device for Fischer-Tropsch synthesis, comprising agasification device 1, an electrolyzer 2, a first gas washing device 3and a Fischer-Tropsch synthesis reactor 4, where the gasification device1 is a gasifier, which may be a Luigi gasifier, a Texaco gasifier, aShell gasifier or a Hangtian gasifier, and comprises a raw materialinlet 1-2, an oxidant inlet 1-3, a water inlet 1-4 and a syngas outletend 1-1; the electrolyzer 2 comprises a hydrogen outlet 2-1, a causticsolution outlet 2-2, a chlorine outlet 2-3 and a saturated NaCl solutioninlet 2-4; the Fischer-Tropsch synthesis reactor 4 comprises a feed gasinlet 4-1, a synthetic product outlet 4-2, an effluent and waste outlet4-3 and an flue gas outlet 4-4; the first gas washing device 3 comprisesa gas inlet 3-1, a gas outlet 3-2, a washing solution inlet 3-3 and abyproduct outlet 3-4; a second gas washing device 5 comprises a gasinlet 5-1, a gas outlet 5-2 and a washing solution inlet 5-3. The syngasoutlet end 1-1 of the gasification device 1 is connected to the gasinlet 3-1 of the first gas washing device 3 via the pipe system, and thegas outlet 3-2 of the first gas washing device 3 is connected to thefeed gas inlet 4-1 of the Fischer-Tropsch synthesis reactor 4 via thepipe system; the hydrogen outlet 2-1 of the electrolyzer 2 is alsoconnected to the feed gas inlet 4-1 of the Fischer-Tropsch synthesisreactor 4 via the pipe system, and the caustic soda solution outlet 2-2of the electrolyzer 2 is connected to the washing solution inlet 3-3 ofthe first gas washing device 3 via the pipe system; the caustic sodasolution outlet 2-2 of the electrolyzer 2 is further connected to awashing solution inlet 5-3 of the second gas washing device 5 via thepipe system, the gas inlet 5-1 of the second gas washing device isconnected to a pipe 7 of waste gas or other CO₂-containing gases, andthe gas outlet 5-2 of the second gas washing device 5 is connected to adownstream process pipe 8 or atmosphere. The first gas washing device 3and the second gas washing device 5 therein are respectively a packedtower, a sieve plate tower or a spray tower.

FIG. 2 shows another device for Fischer-Tropsch synthesis, which is amodified structure of FIG. 1, and comprises a gasification device 1, anelectrolyzer 2, a decarburization device 6, a first gas washing device 3and a Fischer-Tropsch synthesis reactor 4, where a syngas outlet end 1-1of the gasification device 1 is connected to a crude syngas inlet 6-1 ofthe decarburization device 6 via the pipe system, a pure syngas outlet6-3 of the decarburization device 6 is connected to a feed gas inlet 4-1of the Fischer-Tropsch synthesis reactor 4 via the pipe system, a carbondioxide outlet 6-2 of the decarburization device 6 is connected to a gasinlet 3-1 of the first gas washing device 3 via the pipe system; ahydrogen outlet 2-1 of the electrolyzer 2 is also connected to the feedgas inlet 4-1 of the Fischer-Tropsch synthesis reactor 4 via the pipesystem, and a caustic soda solution outlet 2-2 of the electrolyzer 2 isconnected to a washing solution inlet 3-3 of the first gas washingdevice 3 via the pipe system; the caustic soda solution outlet 2-2 ofthe electrolyzer 2 is further connected to a washing solution inlet 5-3of a second gas washing device 5 via the pipe system, a gas inlet 5-1 ofthe second gas washing device 5 is connected to a pipe 7 of waste gas orother CO₂-containing gases, and a gas outlet 5-2 of the second gaswashing device 5 is connected to a downstream process pipe 8 oratmosphere. The first gas washing device 3 and the second gas washingdevice 5 therein are respectively a packed tower, a sieve plate tower ora spray tower; and the decarburization device 6 is a pressure swingadsorption device or a low-temperature methanol washing device.

The technical process of the device for Fischer-Tropsch synthesis shownin FIG. 1 comprises the following steps: the raw material, oxidant andwater for Fischer-Tropsch synthesis are introduced to the gasificationdevice 1 for gasification respectively from the raw material inlet 1-2,the oxidant inlet 1-3 and the water inlet 1-4 of the gasification device1 to obtain a crude syngas with the main components of H₂, CO and CO₂,the compositions of which are CO: 5 to 60%, H₂: 5 to 45% and CO₂: 5 to30% on a dry basis, and the balance is inevitable impurity gases. Crudesyngas output from the syngas outlet end 1-1 of the gasification device1 enters the first gas washing device 3 from the gas inlet 3-1 of thefirst gas washing device 3. At the same time, saturated NaCl solution iselectrolyzed into hydrogen, chlorine and NaOH solution in theelectrolyzer 2, the NaOH solution generated through electrolysis isintroduced via the caustic soda solution outlet 2-2 into the first gaswashing device 3 from the washing solution inlet 3-3 of the first gaswashing device 3 to obtain a pure syngas through removing CO₂ in a crudesyngas. At the same time, the generated NaHCO₃ and Na₂CO₃ solution isdischarged from the by-product outlet 3-4 of the first gas washingdevice 3, and is sold or used as a solid product after concentration andcrystallization. The remaining NaOH solution after absorbing the crudesyngas can be used for removing CO₂ in an industrial waste gas or gasesgenerated in other processes. In addition, at the same time, H₂ obtainedthrough chloralkali is insufflated into the pure syngas to adjust thecarbon/hydrogen mole ratio (CO/H₂) in the pure syngas to 1:1.5 to 2.5according to the requirements of hydrogen flow rate control inFischer-Tropsch synthesis, and then the pure syngas is input into theFischer-Tropsch synthesis reactor 4 from the feed gas inlet 4-1 of theFischer-Tropsch synthesis reactor 4 to produce corresponding liquidhydrocarbons and paraffin products through synthetic reaction. Liquidhydrocarbon products obtained through the reaction are output from thesynthetic product outlet 4-2, effluent and waste flow out from theeffluent and waste outlet 4-3, and flue gas is emitted from the flue gasoutlet 4-4. Please see Examples 1 to 3 for detailed technical operationprocess.

The difference between the technical process shown in FIG. 2 and thetechnical process shown in FIG. 1 is that in FIG. 1, the pure syngas isobtained through removing CO₂ in the crude syngas by direct fullgas-liquid contact between the NaOH solution and the crude syngas, whilein FIG. 2, the pure syngas is obtained through centralized separation ofCO₂ in the crude syngas, and then CO₂ obtained through centralizedseparation is absorbed using the NaOH solution. Please see Examples 4 to6 for detailed technical operation process.

In addition, the NaOH solution generated through electrolysis in theelectrolyzer 2 may no longer be used to absorb CO₂ in the crude syngasor flue gas, and the entire set of chloralkali device is only used toadjust the carbon/hydrogen mole ratio in the syngas as a hydrogensource.

EXAMPLE 1

A normal pressure biomass gasifier is employed, with biomass as rawmaterial, air as an oxidant, the flow rate of the syngas is 8200 kmol/h,the composition of the syngas on a dry basis is (mol. %): CO: 23.28%,H₂: 8.65%, CO₂: 16.82%, N₂: 50.19%, Ar: 0.65%, and other impurity gases:0.41%.

Refer to FIG. 1, the technical process is described as follows: the flowrate of the raw material NaCl solution in the chloralkali process iscontrolled at 5454.81 kmol/h, the NaOH solution obtained therefrom isused to wash the syngas and absorb CO₂ therein to obtain a pure syngas.2759.14 kmol/h NaOH solution is consumed in this process, and theremaining NaOH (2695.67 kmol/h) is used to absorb the flue gas; H₂obtained from the chloralkali process is mixed with the pure syngasafter gas washing to adjust the hydrogen/carbon ratio in the syngas,then the mixed gas is used as the feed gas for Fischer-Tropschsynthesis, and Cl₂ obtained from the chloralkali process is converted toliquid chlorine for sale, where the H₂ content (mol. %) is 10.4% in thepure syngas after gas washing, and is 35.99% in the feed gas forFischer-Tropsch synthesis.

The CO₂ absorption rate in the syngas reaches 99%, and CO/H₂ is 1:1.8 inthe feed gas for Fischer-Tropsch synthesis.

EXAMPLE 2

A normal pressure biomass gasifier is employed, with biomass as rawmaterial, 98% (mol. %) O₂ as an oxidant, the flow rate of the syngas is8200 kmol/h, the compositions of the syngas on a dry basis is (mol. %):CO: 48.10%, H₂: 23.29%, CO₂: 20.84%, N₂: 3.56%, and other impuritygases: 4.20%.

Refer to FIG. 1, the technical process is described as follows: the flowrate of the raw material NaCl solution in the chloralkali process iscontrolled at 10380.08 kmol/h, the NaOH solution obtained therefrom isused to wash the syngas and absorb CO₂ therein to obtain a pure syngas.1708.88 kmol/h NaOH solution is consumed in this process, and theremaining NaOH (8671.20 kmol/h) is used to absorb the flue gas; H₂obtained from the chloralkali process is mixed with the pure syngasafter gas washing to adjust the hydrogen/carbon ratio in the syngas,then the mixed gas is used as the feed gas for Fischer-Tropschsynthesis, and Cl₂ obtained from the chloralkali process is converted toliquid chlorine for sale, where the H₂ content (mol. %) is 29.43% in thepure syngas after gas washing, and is 60.78% in the feed gas forFischer-Tropsch synthesis.

The CO₂ absorption rate in the syngas reaches 99%, and CO/H₂ is 1:1.8 inthe feed gas for Fischer-Tropsch synthesis.

EXAMPLE 3

A normal pressure Texaco gasifier is employed. Coarse coal as rawmaterial and 99% (mol. %) O₂ as an oxidant are mixed with water to yieldwater coal slurry which is then put into the gasifier. The flow rate ofthe syngas is 23622 kmol/h, the compositions of the syngas on a drybasis is (mol. %): CO: 40.28%, H₂: 48.28%, CO₂: 7.94%, N₂: 3.10%, andother impurity gases: 0.40%.

Refer to FIG. 1, the technical process is described as follows: the flowrate of the raw material NaCl solution in the chloralkali process iscontrolled at 13347.37 kmol/h, the NaOH solution obtained therefrom isused to wash the syngas and absorb CO₂ therein to obtain a pure syngas.3751.17 kmol/h NaOH solution is consumed in this process, and theremaining NaOH (9596.20 kmol/h) is used to absorb the flue gas; H₂obtained from the chloralkali process is mixed with the pure syngasafter gas washing to adjust the hydrogen/carbon ratio in the syngas,then the mixed gas is used as the feed gas for Fischer-Tropschsynthesis, and Cl₂ obtained from the chloralkali process is converted toliquid chlorine for sale, where the H₂ content (mol. %) is 52.44% in thepure syngas after gas washing, and is 63.61% in the feed gas forFischer-Tropsch synthesis.

The CO₂ absorption rate in the syngas reaches 99%, and CO/H₂ is 1:1.9 inthe feed gas for Fischer-Tropsch synthesis.

EXAMPLE 4

A normal pressure biomass gasifier is employed, with biomass as rawmaterial, air as a combustion improver, the flow rate of the syngas is8200 kmol/h, the compositions of the syngas on a dry basis is (mol. %):CO: 23.28%, H₂: 8.65%, CO₂: 16.82%, N₂: 50.19%, Ar: 0.65%, and otherimpurity gases: 0.41%.

Refer to FIG. 2, the technical process is described as follows: the flowrate of the raw material NaCl solution in the chloralkali process iscontrolled at 5454.81 kmol/h, the NaOH solution obtained therefrom isused to absorb CO₂ resulting from a pressure swing adsorptivedecarburization of the syngas to yield a pure syngas. 2759.14 kmol/hNaOH solution is consumed in this process, and the remaining NaOH(2695.67 kmol/h) is used to absorb the flue gas; H₂ obtained from thechloralkali process is mixed with the pure syngas after gas washing toadjust the hydrogen/carbon ratio in the syngas, then the mixed gas isused as the feed gas for Fischer-Tropsch synthesis, and Cl₂ obtainedfrom the chloralkali process is converted to liquid chlorine for sale,where the H₂ content (mol. %) is 10.4% in the pure syngas after gaswashing, and is 35.99% in the feed gas for Fischer-Tropsch synthesis.

The CO₂ absorption rate in the syngas reaches 99%, and CO/H₂ is 1:1.8 inthe feed gas for Fischer-Tropsch synthesis.

EXAMPLE 5

A normal pressure biomass gasifier is employed, with biomass as rawmaterial, air as a combustion improver, the flow rate of the syngas is8200 kmol/h, the compositions of the syngas on a dry basis is (mol. %):CO: 48.10%, H₂: 23.29%, CO₂: 20.84%, N₂: 3.56%, and other impuritygases: 4.20%.

Refer to FIG. 2, the technical process is described as follows: the flowrate of the raw material NaCl solution in the chloralkali process iscontrolled at 10380.08 kmol/h, the NaOH solution obtained therefrom isused to absorb CO₂ resulting from a pressure swing adsorptivedecarburization of the syngas to obtain a pure syngas. 1708.88 kmol/hNaOH solution is consumed in this process, and the remaining NaOH(8671.2 kmol/h) is used to absorb the flue gas; H₂ obtained from thechloralkali process is mixed with the pure syngas after gas washing toadjust the hydrogen/carbon ratio in the syngas, then the mixed gas isused as the feed gas for Fischer-Tropsch synthesis, and Cl₂ obtainedfrom the chloralkali process is converted to liquid chlorine for sale,where the H₂ content (mol. %) is 29.43% in the pure syngas after gaswashing, and is 60.78% in the feed gas for Fischer-Tropsch synthesis.

The CO₂ absorption rate in the syngas reaches 99%, and CO/H₂ is 1:1.8 inthe feed gas for Fischer-Tropsch synthesis.

EXAMPLE 6

A normal pressure Texaco gasifier is employed. Coarse coal as rawmaterial and 99% (mol. %) O₂ as an oxidant are mixed with water to yieldwater coal slurry which is then put into the gasifier, the flow rate ofthe syngas is 23622 kmol/h, the compositions of the syngas on a drybasis is (mol. %): CO: 40.28%, H₂: 48.28%, CO₂: 7.94%, N₂: 3.1%, andother impurity gases: 0.40%.

Refer to FIG. 2, the technical process is described as follows: the flowrate of the raw material NaCl solution in the chloralkali process iscontrolled at 13347.37 kmol/h, the NaOH solution obtained therefrom isused to absorb CO₂ resulting from decarburization of the syngas usinglow temperature methanol to yield a pure syngas. 3751.17 kmol/h NaOHsolution is consumed in this process with, and the remaining NaOH(9596.20 kmol/h) is used to absorb the flue gas; H₂ obtained from thechloralkali process is mixed with the pure syngas after gas washing toadjust the hydrogen/carbon ratio in the syngas, then the mixed gas isused as the feed gas for Fischer-Tropsch synthesis, and Cl₂ obtainedfrom the chloralkali process is converted to liquid chlorine for sale,where the H₂ content (mol. %) is 52.44% in the pure syngas after gaswashing, and is 63.61% in the feed gas for Fischer-Tropsch synthesis.

The CO₂ absorption rate in the syngas reaches 99%, and CO/H₂ is 1:1.9 inthe feed gas for Fischer-Tropsch synthesis.

Unless otherwise indicated, the numerical ranges involved in theinvention include the end values. While particular embodiments of theinvention have been shown and described, it will be obvious to thoseskilled in the art that changes and modifications may be made withoutdeparting from the invention in its broader aspects, and therefore, theaim in the appended claims is to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

The invention claimed is:
 1. A method for Fischer-Tropsch synthesis, themethod comprising: 1) gasifying a raw material to obtain a crude syngascomprising H₂, CO and CO_(2;) 2) electrolyzing a saturated NaCl solutionusing a chloralkali process to obtain a NaOH solution, Cl₂, and H₂, 3)separating the CO₂ from the crude syngas to obtain separated CO₂ and afirst gaseous mixture, and then absorbing the separated CO₂ using theNaOH solution obtained in 2); and 4) adding the H₂ obtained in 2) intothe first gaseous mixture to obtain a second gaseous mixture, and thenusing the second gaseous mixture for Fischer-Tropsch synthesis reaction.2. The method of claim 1, wherein in 3), a remaining of the NaOHsolution after absorbing the separated CO₂ is condensed and crystallizedas a by-product.
 3. The method of claim 1, wherein in 3), a remaining ofthe NaOH solution after absorbing the separated CO₂ is used for removingCO₂ in an industrial waste gas or gases generated in other processes. 4.The method of claim 1, wherein in 4), a mole ratio of CO/H₂ in thesecond gaseous mixture is adjusted to 1:1.5 to 2.5.
 5. The method ofclaim 1, wherein in 1), the crude syngas comprises CO: 5-60 mol. %, H₂:5-45 mol. %, CO₂: 5-30 mol. % on a dry basis, and the balance isimpurity gases.
 6. The method of claim 1, wherein in 1), the rawmaterial is coal, biomass, heavy oil, natural gas, agroforestry waste,household waste, or a mixture thereof.